Method and system for performing interspinous space preparation for receiving an implant

ABSTRACT

A method and system are provided for preparing an interspinous space to receive an implantable device. The system may comprise a cutting tool guide having a guiding surface for directing a cutting tool therethrough and a holder for positioning the cutting tool guide relative to the interspinous space. The holder may be configured to adjustably attach to at least one of a pair of spinous processes defining the interspinous space.

This application claims priority under 35 U.S.C. §119 based on U.S.Provisional Application No. 60/774,571, filed Feb. 17, 2006, thecomplete disclosure of which is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a method and system for preparing asurgical site for receiving an implantable device. Specifically, thepresent invention relates to a method and system for preparing theinterspinous space, including the spinous processes, for receiving aninterspinous stabilization device.

BACKGROUND OF THE INVENTION

Conventional methods for implanting interspinous devices provide littleor no control over the exact positioning of the device in animplantation site. Typically, if the surgeon desires more surfacecontact between the device and the bony surface of the spinousprocesses, the surgeon can remove bone tissue using a cutting tool suchas, for example, a chisel, luer plier, or power cutting tool. However,these freestyle methods do not allow precise shaping or contouring ofthe spinous processes, nor do they provide exact control over thepositioning of the device. Improper or incorrect placement of the devicemay lead to less than optimal results, including failure of the device,resulting in detrimental effects to the patient. When using interspinousdevices to treat multiple vertebral levels, proper alignment is evenmore critical to ensure a desirable outcome.

There is thus a need for a system and method for preparing theimplantation site for receiving an implantable device. More importantly,there is a need for a system and method that allow precise control overthe shaping or contouring of the interspinous space and proper insertionof the implantable device into that space.

SUMMARY OF THE INVENTION

A first aspect of the present invention includes a system for preparingan implantation space. The system may be used to guide a bone cuttingtool to enable accurate and controlled shaping or contouring of thespinous processes defining an interspinous space. In one exemplaryembodiment, a system is provided for preparing an interspinous space toreceive an implantable device. The system may comprise a cutting toolguide having a guiding surface for directing a cutting tool therethroughand a holder for positioning the cutting tool guide relative to theinterspinous space. The holder may be configured to adjustably attach toa bony structure of a patient's spine. In one exemplary embodiment, theholder may be attachable to at least one of a pair of spinous processesdefining the interspinous space.

A second aspect of the present invention includes a method for preparingan implantation site. The method may allow preparation of aninterspinous space for receiving an implantable device. In one exemplaryembodiment, a method is provided which involves selecting an implantabledevice for placement in the interspinous space, positioning a cuttingtool guide between a pair of spinous processes defining the interspinousspace, shaping at least one of the pair of spinous processes, andinserting the implantable device into the shaped interspinous space.

A third aspect of the present invention provides a method for guidedshaping of a spinous process. In one exemplary embodiment, a method isprovided which involves positioning a cutting tool guide adjacent aspinous process, the cutting tool guide comprising a guiding surface fordirecting a cutting tool therethrough, and directing a cutting toolagainst the guiding surface and into the spinous process to shape thespinous process.

A forth aspect of the present invention includes a cutting tool guide.The cutting tool guide may be used to guide a bone cutting tool toenable accurate and controlled shaping or contouring of the spinousprocesses defining an interspinous space. In one exemplary embodiment,the cutting tool guide may comprise a main body portion having first andsecond side walls parallel to one another, each side wall having firstand second ends, an inner surface, and an outer surface, and an end wallconnecting the first ends of the first and second side walls to oneanother such that the inner surfaces of the side walls face one another.The cutting guide tool may further comprise at least one pair of guidingslots configured to receive side edges of a cutting tool, wherein oneslot of the pair is on the inner surface of the first side wall and theother slot of the pair is on the inner surface of the second side wall.

A fifth aspect of the present invention provides a method for guidedshaping of a spinous process. In one exemplary embodiment, a method isprovided which involves positioning a cutting tool guide adjacent aspinous process, the cutting tool guide comprising a pair of parallelwalls, each wall having first and second ends and at least one guidingslot for directing a cutting tool therethrough, and directing a cuttingtool through one of the at least one guiding slots on each of theparallel walls and into the spinous process to shape the spinousprocess.

A sixth aspect of the present invention includes a bone cutting tool forpreparing an implantation space. The bone cutting tool may be usedaccurately shape or contour the spinous processes defining aninterspinous space. In one exemplary embodiment, a bone cutting tool isprovided for preparing an interspinous space to receive an implantabledevice. The bone cutting tool may comprise a main body portion havingfirst and second side walls and a front wall portion, the front wallportion configured to contact a bony surface to be shaped and a cuttingelement configured to shape the bony surface, the cutting elementpositioned between the first and second side walls on a front portion ofthe main body. In one exemplary embodiment, the front wall portion liesin a first plane and the cutting element lies in a second plane parallelto the first plane and spaced away from the first plane.

A seventh aspect of the present invention includes a bone cutting toolfor preparing an implantation space. The bone cutting tool may be usedaccurately shape or contour the spinous processes defining aninterspinous space. In one exemplary embodiment, a bone cutting tool isprovided for preparing an interspinous space to receive an implantabledevice. The bone cutting tool may comprise a main body portion havingfirst and second side walls, a rear wall, and a front wall portion, thefront wall portion configured to contact a bony surface to be shaped anda cutting element configured to shape the bony surface, the cuttingelement positioned between the first and second side walls on a frontportion of the main body. In one exemplary embodiment, the front wallportion is positioned a first distance from the rear wall and whereinthe cutting element is positioned a second distance, greater than thefirst distance, from the rear wall.

An eighth aspect of the present invention provides a method for guidedshaping of a spinous process. In one exemplary embodiment, a method isprovided which involves providing a cutting tool having a cutting guidesurface, determining an amount of thickness T to remove from a spinousprocess, positioning a cutting tool cutting element relative to thecutting tool guide surface such that there is a distance T between aplane in which the guide surface lies and a plane in which the cuttingelement lies, positioning the cutting tool guide surface adjacent aspinous process, and moving the cutting tool guide surface and thecutting tool cutting element over the spinous process such that thecutting tool cutting element engages any bony material that extendswithin the distance T between the cutting guide surface and the cuttingtool cutting element

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory only,and are not restrictive of the invention, as claimed.

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate several embodiments of theinvention and together with the description, serve to explain theprinciples of the invention.

Additional objects and advantages of the invention will be set forth inpart in the description which follows or may be learned by practice ofthe invention. The objects and advantages of the invention will berealized and attained by means of the elements and combinationsparticularly pointed out in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a perspective view of a cutting tool guide, accordingto an exemplary disclosed embodiment.

FIG. 2 illustrates a side view of the guide of FIG. 1 and a guideholder, according to an exemplary disclosed embodiment.

FIG. 3 illustrates a side view of the guide of FIG. 2 attached to theguide holder of FIG. 2 in a closed configuration, according to anexemplary disclosed embodiment.

FIG. 4 illustrates a side view of the guide of FIG. 2 attached to theguide holder of FIG. 2 in an open configuration, according to anexemplary disclosed embodiment.

FIG. 5 shows a perspective view of the guide holder with attached guideof FIG. 4, according to an exemplary disclosed embodiment.

FIG. 6 illustrates a perspective view of a bone cutting tool useful withthe exemplary disclosed guide holder and attached guide, according to anexemplary disclosed embodiment.

FIG. 7 illustrates a step in an exemplary method for preparing theinterspinous space using the exemplary disclosed guide holder andattached guide.

FIG. 8 illustrates another step in an exemplary method for preparing theinterspinous space using the exemplary disclosed guide holder andattached guide.

FIG. 9 illustrates yet another step in an exemplary method for preparingthe interspinous space using the exemplary disclosed guide holder andattached guide.

FIG. 10 illustrates still yet another step in an exemplary method forpreparing the interspinous space using the exemplary disclosed guideholder and attached guide.

FIG. 11 illustrates even still yet another step in an exemplary methodfor preparing the interspinous space using the exemplary disclosed guideholder and attached guide.

FIG. 12 illustrates a further step in an exemplary method for preparingthe interspinous space using the exemplary disclosed guide holder andattached guide.

FIG. 13 illustrates a perspective view of an alternative cutting toolguide and a bone cutting tool useful with the alternative cutting guidetool, according to an exemplary disclosed embodiment.

FIG. 14 illustrates a perspective view of a body portion of the cuttingtool guide of FIG. 13, according to an exemplary disclosed embodiment.

FIG. 15 illustrates a perspective view of the cutting tool guide and thebone cutting tool of FIG. 13 with the bone cutting tool being positionedwithin a guiding slot of the cutting tool guide, according to anexemplary disclosed embodiment.

FIG. 16 illustrates a step in an exemplary method for preparing theinterspinous space using the exemplary disclosed cutting tool guide anda cutting tool.

FIG. 17 illustrates a perspective view of a bone cutting tool withcutting guide, according to an exemplary disclosed embodiment.

FIG. 18 illustrates a perspective front view of a body portion of thebone cutting tool with cutting guide of FIG. 17, according to anexemplary disclosed embodiment.

FIG. 19 illustrates a perspective rear view of a body portion of thebone cutting tool with cutting guide of FIG. 17 with a rear panel of thetool in an open position, according to an exemplary disclosedembodiment.

FIG. 20 illustrates a cross sectional view of a body portion of the bonecutting tool with cutting guide of FIG. 17, according to an exemplarydisclosed embodiment.

FIG. 21 illustrates a cross sectional view of a lower body portion ofthe bone cutting tool with cutting guide of FIG. 17, according to anexemplary disclosed embodiment.

FIG. 22 illustrates a step in an exemplary method for preparing theinterspinous space using the exemplary disclosed bone cutting tool withcutting guide of FIG. 17.

DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

FIG. 1 illustrates an exemplary embodiment in which a cutting tool guide20 includes a main body 22 having an aperture 24 extending therethrough.A portion of the aperture 24 is defined by a guiding surface 26. In oneaspect of the invention, the cutting tool guide 20 includes two shapedguiding surfaces 26 that complement an outer surface of a cutting tool,such as for example, a blade 54 of a chisel 50 shown in FIG. 6. Theguiding surfaces 26 serve as a predefined rail or slot in the cuttingtool guide 20, against which the surgeon may direct the chisel 50 intothe implantation site.

The cutting tool guide 20 may also include handles 28 for manipulatingthe guide 20 during use. The handles 28 may be shaped for easy grippingwith fingers. The main body 22 may also include a depressible tab 30formed on a side thereof. The depressible tab 30 may be defined by apair of slots 32 located on the main body 22. A notch 34 may be includedon the depressible tab 30 to allow the cutting tool guide 20 to latchonto a guide holder 60, shown in FIG. 2.

The main body 22 of cutting tool guide 20 may also include an opening 36for insertion of a radiopaque marker 38. As shown in FIG. 1, the cuttingtool guide 20 may include a pair of openings 36 configured as boresextending into the main body 22. The radiopaque markers 38 may beconfigured with a complementary shape, such as a rod as illustrated, forinsertion into the openings 36. When inserted, the radiopaque markers 38provide visual identification of the proper cutting line and depth underfluoroscopy, thereby allowing additional control over alignment duringthe implantation site preparation process. The radiopaque markers 38 areconfigured to align with the cutting edge of the blade 54 of the chisel50 once placed through the guiding surface 26.

FIG. 2 shows a cutting tool guide holder 60, according to an exemplarydisclosed embodiment. The guide holder 60 includes a base 62 into whichthe cutting tool guide 20 may be inserted. When attached, the cuttingtool guide 20 is configured to fit snugly inside the base 62, with thenotch 34 and the depressible tab 30 of the cutting tool guide 20latching onto the base 62 of the guide holder 60.

The guide holder 60 may further include a pair of clamps 64. As shown ingreater detail in FIGS. 3 and 4, each clamp 64 comprises a pair of jaws66, with each jaw 66 extending into a handle portion 68. The jaws 66 arejoined together at a pivot joint 70, thereby forming a scissor-likeconnection. By moving the handle portions 68 closer together or fartherapart, the surgeon or user may adjust the clamping force of the jaws 66.Further, a biasing mechanism 72 may be disposed between the pair ofhandle portions 68 such that compression and distraction of the handleportions 68 relative to one another effects the movement of the jaws 66towards or away from each other. As illustrated, the biasing mechanism72 comprises a spring-like element, such as for example, a leaf spring74. A ratchet 76 is also provided between the handle portions 68 toallow the resistance between the jaws 66 to be adjusted and also locked.The ratchet 76 latches onto a groove 78 located on the opposed handleportion 68, as shown in FIG. 5. The ratchet 76 allows the surgeon oruser to adjust the clamping force between the jaws 66 in increments. Torelease the jaws 66, the ratchet 76 can simply be lifted away from thegroove 78 to allow the handle portions 68 to spread and force the jaws66 apart.

It is contemplated that the clamps 64 of the guide holder 60 may have adifferent configuration so long as the function of securing the guideholder 60 to a bony structure of the spine is preserved. For example,the clamps 64 may be configured as a wrench-like device, with a lockingnut element for securing the wrench-like device onto bone. Othermechanisms for securing the holder to bone may be implemented withoutdeparting from the spirit of the invention. For example, jaws 66 mayinclude various surface modifications that facilitate secure attachmentto bone. Such surface modifications may include, for example, barbs,teeth 80 (as shown in FIG. 3), and/or surface roughening.

FIG. 6 illustrates a chisel-like cutting tool 50 useful with the cuttingtool guide 20, according to an exemplary embodiment. The chisel 50includes a handle portion 52 extending into a cutting blade 54. Thecutting blade 54 may include a shoulder portion 56 that is positioned toabut the cutting tool guide 20 when fully inserted therein. The shoulderportion 56 acts as a stop, preventing overextension of the cutting blade54 through the cutting tool guide 20. Of course, it is contemplated thatother known cutting tools may be utilized with the cutting tool guide 20and guide holder 60 of the present invention.

The cutting tool guide and holder system of FIGS. 1-6 may be utilized inthe preparation of an implantation site to receive an implantabledevice. An exemplary method of preparing an interspinous space forimplantation of an interspinous device using the cutting tool guide andholder system described above is illustrated in FIGS. 7-12.

To use the cutting tool guide and holder system, a surgeon may firstselect one or more vertebral levels to be treated. Based on patientcharacteristics and the surgeon's preference, the surgeon will thenselect the implant to be used. Before implanting the device, the surgeonmay wish to determine the dimensions of the interspinous space where thedevice is to be placed and compare that to the size of the device to beimplanted. To do so, the surgeon may elect to place a series of trials90 into the interspinous space, as is conventionally known to be done,until the proper size and device orientation has been determined, asshown in FIG. 7.

Next, the surgeon may place a cutting tool guide 20 having an aperture24 corresponding in size and shape to the trial 90 onto a guide holder60, and slip the two over the trial 90, as shown in FIG. 8. The surgeonmay manipulate and orient the guide holder 60 over the surgical site andattach the clamps 64 onto the pair of spinous processes 10, 12 definingthe interspinous space. Because the guide holder 60 and cutting toolguide 20 are positioned with respect to the implantation site using thetrial 90, as shown in FIG. 9, the guide holder 60 and cutting tool guide20 are aligned to properly receive the cutting tool.

Removing the trial 90 and then the cutting tool guide 20, as shown inFIG. 10, and leaving the guide holder 60 attached to the spinousprocesses 10, 12, the surgeon may then select a second cutting toolguide 40, as shown in FIG. 11, for insertion into the guide holder 60.The second cutting tool guide 40 may be similar in all aspects to thefirst cutting tool guide 20, except that the aperture 44 is of adifferent size and/or shape than the aperture 24 of the first cuttingtool guide 20. Once the second cutting tool guide 40 is in place, thesurgeon may then insert a cutting tool matching the shape and/or size ofthe implantable device, such as for example, the chisel 50 shown inFIGS. 6 and 12, and use a guiding surface 46 of the cutting tool guide40 to direct the blade 54 into the spinous process 10. If desired, thechisel 50 may be removed and inserted into the guiding surface 46 on theopposing side of the cutting tool guide 40, to thereby shape or contourthe other spinous process 12 of the pair. It is understood that aplurality of cutting tool guides 20, 40 having differently-sized and/orshaped apertures 24, 44 may be provided in order to accommodatevariously sized and/or shaped patient anatomies.

The cutting tool guide and holder system of the present inventionenables accurate and controlled shaping or contouring of the spinousprocesses defining an interspinous space for receiving an implantabledevice. The cutting tool guide 20, 40 enables the cutting tool to bedirected into bone in a specific and controlled manner, while theradiopaque markers 38 also allow visual confirmation of the propercutting line and depth when used under fluoroscopy. Further, the guideholder 60 is flexibly configured to be adjustable in position, cuttingheight, and angle relative to the interspinous space in order tooptimize the ability of the guide holder 60 to be applied to differentlevels of the spine for multi-level or multi-segmental applications ofthe interspinous implantable device.

It is contemplated that the cutting tool guide and holder system of thepresent invention may be applied using other methods to shape thespinous process. For instance, it is understood that the guide holder 60may be attached to other patient anatomies rather than the spinousprocesses defining the interspinous space. The guide holder 60 may beconfigured to attach to, for example, the lamina or transverse processesof the patient. In addition, it is possible to use the cutting toolguide 20, 40 to direct the angle, depth, and/or position of the cuttingtool without attaching the cutting tool guide 20, 40 to the patient. Ifdesired, the surgeon may simply use the cutting tool guide 20, 40 aloneto align and direct the cutting line of the bone cutting tool.

Further, although a system and method for preparing an interspinousspace is described for use with an interspinous implant, it iscontemplated that the system of the present invention can also beutilized in any application where exact shaping or contouring of thespinous process is desired. For example, it is possible to use thecutting tool guide 20, 40 and guide holder 60 to direct shaping and/orcontouring of the spinous process for decompression.

FIG. 13 illustrates an alternative exemplary embodiment of a cuttingtool guide. The cutting tool guide 120 includes a main body 122 havingfirst and second side walls 124 a and 124 b. First and second side walls124 a, 124 b are substantially parallel to one another, are spaced awayfrom one another, and are connected by a third wall 126. The unconnectedends of the first and second side walls 124 a, 124 b form an open end125 of the main body 122 of the cutting guide tool. The open end 125 mayor may not be configured to fit onto or around a spinous process. Innersurfaces 128 a, 128 b of respective first and second side walls 124 a,124 b each include a plurality of slots 130 a, 130 b. The plurality ofslots 130 a, 130 b extend along a height of the inner surfaces 128 a,128 b and are aligned with each other such that the plurality of slots130 a, 130 b form a plurality of guiding slots configured to receive andguide side edges of a cutting tool such as, for example, a blade 154 ofa chisel 150 shown in FIG. 13. The blade 154 of the chisel 150 may beinserted into a space 127 in the main body 122 of the cutting guide tool120 defined by the first and second side walls 124 a, 124 b and thethird wall 126 such that the edges of the blade 154 of the chisel 150fit into and move within guiding slots 130 a, 130 b as shown in FIG. 15.The guiding slots 130 a, 130 b serve to guide the cutting tool bladealong a straight path at the implantation site in order to provide astraight cut along the bone. The chisel may include a shoulder 156 toprevent it from passing too far through the guiding slots 130 a, 130 b.Several different guiding slots 130 a, 130 b are provided to permit thesurgeon to remove as little or as much bone as necessary to provide aninterspinous space of the correct size and with an appropriate surfacesuch as, for example, a surface having an appropriate flatness,smoothness, or planar shape. Thus, for example, by selecting a pair ofguiding slots 130 a, 130 b spaced close to the open end 125 of the mainbody 122, the surgeon can remove only a small amount of bone. Byselecting a pair of guiding slots 130 a, 130 b spaced further away fromthe open end 125 of the main body 122, the surgeon can remove a largeramount of bone. Although it is intended that parallel guiding slots beused to guide the cutting tool in a perpendicular cut, it is alsocontemplated that guiding slots 130 a, 130 b that are not aligned withone another may be used together to provide an angled cut.

As further shown in FIGS. 13 and 14, the main body 122 of the cuttingtool guide 120 includes a lip portion 132 that extends from the thirdwall 126 of the main body 122. The lip portion 132 forms an angle ofapproximately 90 degrees with the third wall 126, such that it forms aright angle with the third wall 126 and extends in a directionperpendicular to the third wall 126. During use of the cutting toolguide 120, the third wall 126 and the lip portion 132 permit the cuttingtool guide 120 to be positioned with respect to one of a pair of spinousprocesses 10, 12 that form the interspinous space, while positioning theopen end of the cutting tool guide 120 such that it abuts the second ofthe pair of spinous processes 10, 12 that forms the interspinous spaceand provides access to the guiding slots 130 a, 130 b adjacent to thesecond spinous process.

The cutting tool guide 120 may be held in place or moved to a differentposition through use of a handle 134. Handle 134 is connected to lipportion 132. As shown in FIGS. 13, 15, and 16, handle 134 may include afirst vertical portion 136 and a second angled portion 138. This permitsa person holding the handle 134 to remain out of the direct field ofvision of the surgical site. The handle 134 may also include a grippingportion 140. Other alternative configurations of the handle 134 are alsopossible, such as a vertical handle, a handle having two verticalportions connected by a horizontal portion, or any other combination ofvertical, angled, and horizontal segments.

The cutting tool guide of FIGS. 13-16 may be utilized in the preparationof an implantation site to receive an implantable device. An exemplarymethod of preparing an interspinous space for implantation of aninterspinous device using the cutting tool guide described above isillustrated in FIG. 16.

To use the cutting tool guide 120 a surgeon may first select one or morevertebral levels to be treated as described previously with respect toFIGS. 7-12. Based on patient characteristics and the surgeon'spreference, the surgeon will then select the implant to be used. Beforeimplanting the device, the surgeon may wish to determine the dimensionsof the interspinous space where the device is to be placed and comparethat to the size of the device to be implanted. To do so, the surgeonmay elect to place a series of trials 90 into the interspinous space, asis conventionally known to be done, until the proper size and deviceorientation has been determined, as was discussed with regard to FIG. 7.

Next, the surgeon may place a cutting tool guide 120 into theinterspinous spaced defined by a pair of spinous processes 10, 12. Asshown in FIG. 16, the handle 134 can be used to manipulate the cuttingtool guide 120 until the third wall 126 is positioned against one of thespinous processes 10, 12, with the lip portion positioned on top of onespinous process 12. The third wall 126 may be visually aligned parallelto the spinous process 12 as shown in FIG. 16. Because the cutting toolguide 120 is positioned with respect to the spinous process 12, as shownin FIG. 16, the open end 125 of the cutting tool guide 20 is alignedwith the other of the spinous processes 10 to properly receive thecutting tool.

When the cutting tool guide 120 is held in position with third wall 126aligned with spinous process 12, the spinous process 10 may becontoured. The surgeon may then insert a cutting tool matching the shapeand/or size of the implantable device, such as for example, the chisel150 shown in FIGS. 13, 15, and 16, and use the guiding slots 130 a, 130b of the cutting tool guide 120 to direct the blade 154 into the spinousprocess 10. Subsequently, if desired, the cutting tool guide 120 may berotated 180 degrees within the interspinous space to align third wall126 with the spinous process 10 and to permit shaping or contouring ofthe other spinous process 12. Use of the chisel 150 in a pair of theguiding slots 130 a, 130 b results in the creation of a substantiallyperfectly parallel interspinous space, improving the fit of an implantand thus reducing contact stresses and bone erosion.

If desired, the chisel 150 may be removed from a first set of guidingslots 130 a, 130 b, the cutting tool guide 120 removed from theinterspinous space (or left in place) and the trial 90 may be reinsertedto judge fit. If necessary, the cutting tool guide can be reinsertedinto the interspinous space and another pair of guiding slots 130 a, 130b used with blade 154 to remove additional bone as needed. Subsequently,if desired, the cutting tool guide 120 may be rotated 180 degrees withinthe interspinous space to permit shaping or contouring of the otherspinous process 12 of the pair. It is understood that a plurality ofcutting tool guides 120 having differently sized and/or shaped spaces127 may be provided in order to accommodate variously sized and/orshaped patient anatomies. Additionally, different cutting tool guides120 having differently spaced guiding slots 130 a, 130 b, or havingguiding slots 130 a, 130 b that are provided in parallel to one anotheror at an angle to one another may also be used.

It is contemplated that the cutting tool guide 120 of the presentinvention may be applied using other methods to shape the spinousprocess. For instance, it is understood that the cutting guide tool 120may be used with portions of the method described with respect tocutting guides 20, 40. In addition, it is possible to use the cuttingtool guide 120 to direct the angle, depth, and/or position of thecutting tool while attaching the cutting tool guide 120 to the patient,for example with guide holder 60.

Further, although a system and method for preparing an interspinousspace is described for use with an interspinous implant, it iscontemplated that the system of the present invention can also beutilized in any application where exact shaping or contouring of thespinous process is desired. For example, it is possible to use thecutting tool guide 120 to direct shaping and/or contouring of thespinous process for decompression.

FIG. 17 illustrates an alternative exemplary embodiment of a bonecutting tool with cutting guide. The bone cutting tool with cuttingguide 200 includes a main body 202 having first and second side walls204 a and 204 b. First and second side walls 204 a, 204 b aresubstantially parallel to one another, are spaced away from one another,and are connected by a top wall 206 a and a bottom wall 206 b. First andsecond side walls 204 a, 204 b are also connected by a partial frontwall 208, as shown in FIGS. 17 and 18. Partial front wall 208 does notextend to bottom wall 206 b such that an opening 210 is formed in afront portion of the main body 202 between partial front wall 208 andbottom wall 206 b. Partial front wall 208 is preferably a planar wallthat acts as a guide, as will be described below.

As shown in FIG. 19, the main body 202 also includes a removable rearpanel 208. As shown in FIG. 19, rear panel 212 may be slidably mountedin grooves provided on inner surfaces of the first and second side walls204 a, 204 b. Rear panel 212 may alternatively be removably mounted onthe rear portion of the main body 202 by an other suitable means, suchas for example, by hinging or by screws. Further, the rear panel may notbe completely removable but simply openable to allow access to theinterior of the main body 202.

As shown in FIG. 18, a blade 220 is adjustably mounted in the opening210 in the front portion of the main body 202. Blade 220 is mounted suchthat the cutting end 222 of the blade is facing the partial front wall208. Blade 220 is parallel to the partial front wall 208 but does notlie in the same plane as the partial front wall 208. Thus, as shown inFIG. 21, blade 220 is positioned a distance T above the partial frontwall 208. Thus, the partial front wall 208 acts as the cutting guide ofthe bone cutting tool as the tool is moved along a bony surface to beshaped or contoured. As the tool is moved along the bony surface, anybone chips extending above the partial front wall 208 encounter thecutting edge 222 of blade 220 and are shaved off. Thus, the cutting toolacts as a planing tool. The distance T between the partial front wall208 and the blade 220 is adjustable to increase or decrease the amountof bone removed with each pass of the cutting tool. As shown in FIGS.19-21, the rear panel 212 permits access to a screw 214 for adjustingthe position of the blade 220 and thus the distance T between thesurface of the partial front wall 208 and the blade 220. Other suitablemeans for adjusting the distance T between the partial front wall 208and the blade 220, such as a movable front wall, may be used.

Alternatively, the position of blade 220 may not be adjustable and thusthe distance T between the surface of the partial front wall 208 and theblade 220 would be fixed for the cutting tool. In such an embodiment,blade 220 may be removable from the main body 202 and replaceable withan alternative blade 220 a, 220 b, 220 c (not shown) having a differentgeometry and providing a different distance T between the surface of thepartial front wall 208 and the blade 220 a, 220 b, 220 c. It is alsoenvisioned that a surgeon could be provided with a plurality of mainbodies 202, each having a blade with a different blade geometry and thusa different distance T between the surface of the partial front wall andthe blade 220. The surgeon could then choose the main body having thedesired cutting thickness T. In such a case, each main body could have ahandle permanently attached, or a detachable handle could be providedfor use with any main body 202.

As also shown in FIGS. 19-21, the walls of the main body 202 form acavity 226 within the main body 202. The cavity 226 is accessiblethrough rear panel 212. The cavity 226 serves to collect bone chips andfragments that are removed by the cutting edge 222 of blade 220 and passthrough the opening 210 between the partial front wall 208 and the blade220.

The bone cutting tool with cutting guide 200 also includes a handle 230.As shown in FIG. 17, the handle may extend from the top wall 206 a. Asshown, the handle may be straight and extend vertically from the top ofthe main body 202. This permits the surgeon to use the handle to pullthe bone cutting tool and cutting guide along the bone surface to beshaped or contoured. The handle 230 may include a gripping portion 232.

To use the bone cutting tool with cutting guide 200, a surgeon may firstselect one or more vertebral levels to be treated. Based on patientcharacteristics and the surgeon's preference, the surgeon will thenselect the implant to be used. Before implanting the device, the surgeonmay wish to determine the dimensions of the interspinous space where thedevice is to be placed and compare that to the size of the device to beimplanted. To do so, the surgeon may elect to place a series of trials90 into the interspinous space, as is conventionally known to be done,until the proper size and device orientation has been determined, as wasdiscussed with regard to FIG. 7.

Once the desired dimensions of the interspinous space are known, thesurgeon may select a surface of the interspinous space for shaping orcontouring. As shown in FIG. 22, the interspinous space is defined bytwo adjacent spinous processes 10, 12. The surgeon may elect to shapeand/or contour the surfaces of one or both of the spinous processesforming the interspinous space. The surgeon adjusts the position of theblade 220 relative to the partial front wall 208 to provide a desireddistance T between the partial front wall 208 that will act as a cuttingguide and the blade 220 that will be the cutting tool. Alternatively,the surgeon can select the appropriate blade 220 that will provide thedesired cutting thickness defined by the distance T between the partialfront wall 208 and the blade 220. The blade 220 may be pre-installed ina main body 202 or may need to be installed by the surgeon.

The surgeon then positions the tool with the front side facing and incontact with the bone surface to be shaped and at a lowermost point ofthe bone surface to be shaped (e.g., the most anterior portion of aspinous process to be shaped). The tool is drawn upward (e.g.,posteriorly along the spinous process) along the bone surface and awayfrom the patient's body, and any bone extending above the cutting guide(partial front wall 208) is cut by blade 220 and passes through opening210 in the front of the tool and into cavity 226. The surgeon can repeatthe process of drawing the tool upward and along the bone surface untilthe desired shape of the bone surface is achieved. If necessary, theback panel 212 may be removed and the bone chips emptied from the cavity226. The process then may be repeated as necessary for the other spinousprocess forming the interspinous space.

Although both the blade 220 and the partial front wall 208 are disclosedas being planar surfaces, it is contemplated that one or both of thesurfaces may be provided with a slight curve or contour to permit avariety of shaping and contouring of the bone surface of theinterspinous space.

Other embodiments of the invention will be apparent to those skilled inthe art from consideration of the specification and practice of theinvention disclosed herein. It is intended that the specification andexamples be considered as exemplary only, with a true scope and spiritof the invention being indicated by the following claims.

1.-15. (canceled)
 16. A method for guided shaping of a spinous process,comprising: positioning a cutting tool guide adjacent a spinous process,the cutting tool guide comprising a guiding surface for directing acutting tool therethrough; and directing a cutting tool against theguiding surface and into the spinous process to shape the spinousprocess.
 17. The method of claim 16, further including the step ofattaching the cutting tool guide to a cutting tool guide holder, theguide holder being configured to adjustably attach to a bony structureof a patient's spine.
 18. The method of claim 17, further including thestep of attaching the guide holder to a bony structure of the patient'sspine.
 19. The method of claim 18, wherein the bony structure is aspinous process, lamina or transverse process.
 20. The method of claim19, further including the step of attaching the guide holder to a pairof spinous processes.
 21. The method of claim 20, further including thestep of shaping both spinous processes of the pair of spinous processes.22. The method of claim 16, further including the step of measuring adimension of an interspinous space defined by a pair of spinousprocesses prior to shaping at least one of the pair of spinousprocesses.
 23. The method of claim 22, wherein the step of measuringcomprises insertion of a trial into the interspinous space.
 24. Themethod of claim 22, further including the step of inserting animplantable device into the interspinous space.
 25. The method of claim16, wherein the step of shaping comprises cutting away bone tissue usingthe cutting tool. 26.-70. (canceled)